It is quite common to provide synchronized audio and visual programs for many purposes such as teaching aids, business presentations and pleasure programming. Whatever use is being made of the visual and audio programs, it is important that the visual presentation be advanced in synchronization with the audio program. Additionally, in various types of teaching devices which employ scanning mechanisms in cooperation with advancing film strips and the like and coordinated audio programs, it is important that all of the related elements be synchronized so that the movement of the film, the audio presentation and the scanning by the light means is coordinated and synchronized under controlled conditions. Naturally in addition to film strips for visual presentation, other perforated materials can be used for a variety of purposes and can be coordinated with audio or other means in a synchronized fashion.
Example of a synchronized audio visual system of the type under consideration is present in U.S. Pat. No. 4,053,214. The contents of that patent are incorporated herein by reference.
In conventional types of known systems such as present in the above referenced patent, the cue signal from the audio tape is detected and activates a relay or other switching device. The closure of the relay contacts connects voltage by a cable to the projector motor circuit which in turn advances the film. In common use, the lead time before film advance for this voltage to reach the motor is approximately 1/2 second. Because the cue signal time is not precise and due to other variables such as mechanical resistance, over travel, and the like which are present, the film advance cannot be equal, nor synchronized. Accordingly, a referenced limit means is necessary on the projector film advance mechanism. Normally this is accomplished by a cam and micro switch or photo cell. This results in a somewhat complex system including a number of additional component parts and wiring requirements. Naturally, assembly and disassembly then takes a greater length of time. It is contemplated that a simpler and equally if not more effective system can be deviced for insuring the synchronization of an audio program, such as that presented on a cassette tape, with a visual projector, such as the teaching film strip projector depicted and described in the above referenced patent.